For most applications, recombinant proteins must be purified in soluble form; however, when expressed in E. coli, many proteins fold aberrantly and become an insoluble aggregate in the cell. We propose to create a genetic method to allow scientists using E. coli for recombinant protein expression to immediately ascertain whether their target is soluble or insoluble. This is done directly without having to grow cultures of these cells and isolate protein. In addition, this method would also comprise a genetic selection for identifying domains or mutants of insoluble proteins that are soluble, making them amenable to downstream applications. 7. PROJECT NARRATIVE A central component towards the understanding of human, animal, and all cell biology is the study of the proteins encoded by the organism. We propose to develop a novel method to accelerate the study of proteins by creating a rapid way to evaluate whether the protein of interest can be immediately purified and studied or whether it needs to be modified before this work can begin. [unreadable] [unreadable] [unreadable]